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Prevention of Type 2 Diabetes. Marshall H. Chin, MD Carol M. Mangione, MD Assoc. Prof. Of Medicine Prof. Of Medicine University of Chicago David Geffen School of Medicine at UCLA. Outline. Background and Study Questions Intervention and Measures 2 Study Designs

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prevention of type 2 diabetes
Prevention of Type 2 Diabetes

Marshall H. Chin, MD Carol M. Mangione, MD

Assoc. Prof. Of Medicine Prof. Of Medicine

University of Chicago David Geffen School of Medicine at UCLA

outline
Outline
  • Background and Study Questions
  • Intervention and Measures
  • 2 Study Designs
    • RCT with randomized encouragement
    • Quasi-experimental with staggered enrollment
  • Tradeoffs
  • Discussion
diabetes in the united states
Diabetes in the United States
  • More than 16 million people in the US have diabetes
  • > 90% have Type 2 diabetes
    • 6% of the population
    • 13% of the population older than age 40
    • 19% of the population older than age 65
  • 35% of persons with diabetes are undiagnosed
  • 798,000 new cases are diagnosed every year

CDC National Diabetes Fact Sheet 1998

estimated growth in type 2 diabetes and us population from 2000 2050
Estimated Growth in Type 2 Diabetes and US Population From 2000-2050

Bagust A, et al. Diabetes 50, Suppl 2 A205, 2001

slide6
Age

Obesity

Body fat distribution

Physical inactivity

Family history of diabetes

Race/ethnicity

Previous gestational diabetes (GDM)

Elevated fasting glucose levels

Impaired glucose tolerance(IGT)

Risk Factors for Type 2 Diabetes

slide7
Weight Gain and Sedentary Life-style Increase Risk of Developing Diabetes
  • Every 1 kilogram (2.2 pounds) of weight
  • gain per 10 years is associated with a
  • 4.5% increased risk to develop diabetes.
  • 68 - 72 % of diabetes risk in the U.S. is
  • attributable to or associated with excess
  • weight.
  • Numerous studies have documented an
  • association between low levels of physical
  • activity and risk to develop diabetes

Ford et al. Amer J Epidemiol 146:214,1997

impaired glucose tolerance
Impaired Glucose Tolerance
  • Major risk factor for cardiovascular disease
  • IGT may be optimal time for intervention
    • Asymptomatic
    • Potentially reversible
    • Diabetes-specific complications have not developed
slide9
Stages in the History of

Type 2 Diabetes

Type 2

Diabetes

Normal

IGT

Disability

Death

Complications

Clinical

disease

Preclinical

state

Complications

20,000,000 16,000,000

Primary Secondary Tertiary

prevention prevention prevention

feasibility of prevention prevention of type 2 diabetes should be feasible since
Feasibility of PreventionPrevention of Type 2 diabetesshould be feasible since:
  • There is a long period of glucose intolerance that precedes the development of diabetes
  • Screening tests can identify persons at high risk
  • There are safe, potentially effective interventions
modifiable risk factors for type 2 diabetes
Modifiable Risk Factors for Type 2 Diabetes
  • Obesity
  • Body fat distribution
  • Physical inactivity
  • Elevatedfasting and 2 hr glucose levels
study interventions
Intensive

Lifestyle

(n = 1079)

Metformin

(n = 1073)

Placebo

(n = 1082)

Study Interventions

Eligible participants

Randomized

Standard lifestyle recommendations

primary outcomes
Primary Outcomes
  • Annual fasting plasma glucose (FPG) and 75 gm Oral Glucose Tolerance Test
    • FPG > 126 mg/dL (7.0 mmol/L) or
    • 2-hr > 200 mg/dL (11.0 mmol/L),

Either confirmed with repeat test

  • Semi-annual FPG
    • > 126 mg/dL, confirmed
screening and eligibility
Screening and eligibility

Number of participants

Step 1 screening

158,177

Step 2 OGTT

30,985

Step 3 start run-in

4,719

Step 3 end run-in

4,080

3,819*

Step 4 randomization

*3,234 in 3 arm study

(585 in troglitazone arm)

lifestyle intervention
Lifestyle Intervention

An intensive program with the following specific goals:

  • > 7% loss of body weight and maintenance of weight loss
    • Fat gram goal -- 25% of calories from fat
    • Calorie intake goal -- 1200-1800 kcal/day
  • > 150 minutes per week of physical activity
lifestyle intervention structure
Lifestyle Intervention Structure
  • 16 session core curriculum (over 24 weeks)
  • Long-term maintenance program
  • Supervised by a case manager
  • Access to Lifestyle support staff
    • Dietitian
    • Behaviorist
    • Exercise physiologist
the core curriculum
The Core Curriculum
  • 16 session course conducted over 24 weeks
  • Education and training in diet and exercise methods and behavior modification skills
  • Emphasis on:
    • Self monitoring techniques
    • Problem solving
    • Individualizing programs
    • Self esteem, empowerment, and social support
    • Frequent contact with case manager and DPP support staff
slide18
Mean Weight Change

+

Placebo

Metformin

Lifestyle

0 6 12 18 24 30 36 42 48

Months

lifestyle intervention19
Lifestyle Intervention

Summary

  • 74% of volunteers assigned to intensive life style achieved the minimum study goal of > 150 minutes of activity per week
  • Mean activity level:
    • At end of core curriculum: 224 minutes
    • At most recent visit: 189 minutes
slide20
Percent developing diabetes

All participants

Lifestyle (n=1079, p<0.001 vs. Met , p<0.001 vs. Plac )

40

Metformin (n=1073, p<0.001 vs. Plac)

Placebo (n=1082)

30

Cumulative incidence (%)

20

10

0

0

1

2

3

4

Years from randomization

pre diabetes
“Pre-diabetes”
  • A new post-DPP term, includes those with:
  • Impaired fasting glucose:
    • FPG 100–125mg/dl (5.6–6.9 mmol/l)
  • Impaired glucose tolerance:
    • 2-h postload glucose 140–199 mg/dl (7.8–11.1mmol/l)
  • 40,000,000 with pre-diabetes!

From the 2004 American Diabetes Association Guideline

background
Background
  • Diabetes Prevention Program (DPP): Intensive lifestyle intervention (diet and exercise) reduces relative risk of DM by 58% over 3 years
  • But, can it be translated to real world settings??
challenge of translating dpp to the community
Challenge of Translating DPP to the Community
  • Enrolling more generalizable population
    • Funnel of study enrollment for DPP
  • Measurement of Impaired glucose tolerance in the community: FBS versus OGTT
  • DPP lifestyle intervention intensive – realistic?
    • Training of study personnel
    • Intensity of intervention and F/U
  • Sustainability
general translation challenges in minority communities
General Translation Challenges in Minority Communities
  • Trust
  • Enrollment
  • Value of the “placebo” or “low intensity” study arm
  • Is losing weight and diabetes prevention a community priority?
primary study question
Primary Study Question
  • Can community interventions designed to increase physical activity and change diet prevent the onset of type 2 diabetes among overweight and obese persons with pre-diabetes?
subquestion
Subquestion
  • What intensity of implementation occurs when organizations are presented with a menu of choices in a program to increase physical activity and cause dietary change?
common elements of study design community based participatory research
Common Elements of Study Design:Community-based Participatory Research
  • Community and researchers are equal partners
  • Build on existing strengths / infrastructure in community
  • Community / patient empowerment
  • Improving community health overriding goal
  • Takes into account community and individual preferences
study population
Study Population
  • Study setting: Churches in African American and Latino communities of Chicago and Los Angeles; Aim 50 people per church
  • Pre-diabetes: Impaired fasting glucose (> 100 to 125 mg/dl), age > 50 yrs, BMI > 30
    • Fallback: Overweight or obese with DM risk factors?
  • Exclusions: DM, severe disability, dementia, short life expectancy
enrollment and study period
Enrollment and Study Period
  • Work with local PIs with longstanding community church ties
  • Pastor
  • Church senior ambassador / opinion leader
    • Respected senior citizen with condition
length of study
Length of Study
  • Intensive intervention: Weekly x 16 weeks
  • Maintenance intervention: Monthly x 8 months
  • Follow-up 3 years
intervention menu of choices physical activity
Intervention: Menu of ChoicesPhysical Activity
  • Goal: Increase walking
    • Guideline goal: 150 minutes/week of walking
    • In practice, patient selects own goals
physical activity menu
Physical Activity Menu
  • Self-monitoring, pedometer
  • Buddy system walking program
  • Group walking sessions
  • Collaborate with local Y or public parks
  • Exercise classes taught by high school / college congregants
  • Other suggested by community participants
  • Particpants are encouraged to select activities from the list that they feel will work best for them
nutrition diet intervention
Nutrition / Diet Intervention
  • Goal: Decrease calories Decrease fat / sugar
  • Goals based upon weight and personal tailoring (Age, BMI, readiness to change)
  • Health educator facilitator and 4-5 volunteer lay coaches
nutrition diet menu
Nutrition / Diet Menu
  • 1-on-1 individual sessions – health educator, lay coach, home visits
  • Group classes
  • Church social marketing campaign
  • Support groups – problem-solving & goal setting
  • Buddy system
  • Involve family
  • Other suggested by community participants
  • Participants are encouraged to select activities from the list that they feel will work best for them
outcome
Outcome
  • Primary – onset of DM (fasting plasma glucose greater than 125 mg/dl)
  • Secondary
    • Physical activity - Weight, BMI
    • Dietary change - Knowledge
    • HgbA1c, lipids - Blood pressure
    • Self-efficacy - Quality of life
process assessment fidelity of the intervention
Process AssessmentFidelity of the Intervention
  • Checklists – content and intensity of intervention
    • When given a choice, what do participants select to participate in?
    • Do certain elements in the intervention have better “uptake”?
  • Qualitative interviews of participants
randomized controlled trials
Randomized Controlled Trials
  • Considered to be the gold standard
    • randomly allocated to either intervention or control group
    • best way to insure that both known and unknown factors that may influence the effectiveness of the intervention are balanced in the 2 comparison groups
  • Time consuming, expensive, complex, may require a large number of clusters, tight inclusion criteria limit generalizabilty
  • Unlikely to tell you whether an intervention will improve routine practice
study design selection
Study Design Selection
  • Challenge is translation research is that the interventions are usually complex (multifaceted with simultaneous changes in different parts of the community)
  • Researcher has variable control over how the intervention is implemented
  • In translation research there can be political, practical, and ethical barriers to randomized designs and other choices may be the best options

Eccles M, et al. Qual Saf Health Care 2003;12;47-52

design 1 randomized encouragement trial ret
Design 1: Randomized Encouragement Trial (RET)
  • Retains experimental structure but emphasizes a pragmatic public health perspective
  • Combines strengths of the RCT and Observational studies
  • Instead of mandating treatment assignment, randomizes participants to encouragement for the target intervention
  • Promotes a more equitable relationship between the researcher and the participant/community

Duan N, et al. Randomized Encouragement Trial: A Pragmatic, Public

Health Oriented Paradigm for Clinical Research. In preparation 2004

randomized encouragement trial ret
Randomized Encouragement Trial (RET)
  • Facilitates participants’ autonomy with regard to treatment decisions -- may be an important feature for sustaining a life style intervention over time
  • Maintains many of the real world aspects of facilitation of behavioral change in community and medical settings.
  • Unit of randomization can be at the participant level or at a higher level
randomized encouragement trial ret41
Randomized Encouragement Trial (RET)
  • Requires recruitment, consent, enrollment, and randomization
  • Intervention group:
    • Randomized to encouragement rather than mandatory treatment assignment
  • Control group:
    • no encouragement
  • Maintaining personal choice, much as one would have to in practice or community settings is a critical element of this design
what is encouragement
What is Encouragement?
  • Offer of resources, incentives, education, and communication (persuasive messages) designed to increase the probability that a participant will want to adopt the treatment
  • Various encouragement strategies can be tested in a bundle, in combinations, or individually
  • Encouragement strategies can be developed collaboratively with communities and the population of interest
why encouragement
Why Encouragement?
  • Attempts to influence treatment adoption through participants’ autonomous choice, leaving ultimate decisions to the participants
  • Choices are voluntary
  • Some participants might reject all menu choices in the intervention, some might select some
  • Some controls may figure out how to get access to the intervention through other means
randomized encouragement trial analyses
Randomized Encouragement Trial Analyses
  • Assuming that the encouragement increases treatment adoption, it can provide an evaluation of treatment effectiveness using an intent-to-treat analysis
  • Provides important qualitative and quantitative findings with regard to adoption and what is desirable and feasible in the community context
  • Pragmatic by nature
    • stronger external validity than the RCT
    • stronger internal validity than observational studies
randomized encouragement trial strengths
Randomized Encouragement Trial Strengths
  • Retains aspects of naturalist treatment delivery
  • May enhance the appeal of participation in effectiveness and translational research by maintaining autonomous choice which will enhance recruitment of more representative samples
  • Rather than viewing treatment choice as a threat to internal validity, it is part of the primary data collection that informs the researcher about participant decision processes
randomized encouragement trial strengths46
Randomized Encouragement Trial Strengths
  • Can provide important information about what can actually be delivered in real world settings
randomized encouragement trial weaknesses
Randomized Encouragement Trial Weaknesses
  • Internal validity is lower than in RCTs but higher than in observational designs
  • By its less controlled nature RETs tend to have smaller effect sizes and greater within group variance therefore require bigger sample sizes.
ret strengths and weaknesses
RET Strengths and Weaknesses

> Moderate dominance, >> strong dominance

Duan N., et al. Personal Communication

ret sample size considerations
RET Sample Size Considerations
  • DPP, assume that the treatment effect is prevention of 6.2 cases of DM per 100 person-years
  • Then in the RET, if adoption Pd=0.5, then RET treatment effect is 3.1 cases of DM per 100 person years
  • Then inflation factor is (1/0.5)2 = 4 times more sample needed for the same power!
design 2 quasi experimental with staggered enrollment
Design 2: Quasi-Experimental with Staggered Enrollment
  • Randomization of initial assignment into intervention or control arm
  • After 1 year, control participants transfer into intervention arm
staggered enrollment analyses
Staggered Enrollment Analyses
  • Intervention vs. control
  • Among control subjects that crossover into intervention, each subject can serve as own control
staggered enrollment strengths
Staggered Enrollment Strengths
  • Increased enrollment compared with std RCT
  • Increased subject retention compared with std RCT
  • Intervention and control subjects drawn from same population
  • Subjects initially randomized to control group can serve as own controls
staggered enrollment weaknesses
Staggered Enrollment Weaknesses
  • Secular trends
  • Possible contamination of control groups
  • Learning effects – control group has 1 more year in study
  • Shorter F/U time in initial control group
ret sample size considerations56
RET Sample Size Considerations

RET:

  • P1 Adoption rate in the intervention group
  • P0 Adoption rate in the control group
  • RET the incremental adoption rate is: Pd = P1-P0

RCT

  • Q1 Adoption rate in the intervention group
  • Q0 Adoption rate in the control group
  • RCT with perfect adherence adoption rate is: Qd = Q1

Assume treatment effect is constant M, then RET intervention effects are PdX M and RCT effects are QdX M and the inflation factor is: (Qd/ Pd )2

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